1986 268 weekender engine speed and planning?

Theres is a range where your WOT should be.
Low end may be 4200rpm and the Max may be 4600rpm
Peek TQ is usually 3600rpm. I would shoot for Max speed at 3600rpm and still have WOT above 4200rpm.
I was thinking the new Vortec/350Mag engines spin up to 5000 rpm? Most likely different cam profile.
I would spend a day dialing in your trim.
Then maybe try getting your prop customized.
There's a term called Blade Area. Too much of that without enough power to spin the prop will yield low WOT rpm. Prop shop would trim some blade off. Making it easier to spin. You stay with the same pitch moving you forward. Call a prop shop.
 
Last edited:
yeah your right the new vortecs are good for 5000 rpm's. Don't know if the alpha can take it thou..lol.. Playing will have to wait till after the holiday. Boat is all packed and ready for the 120 mile trip to the chesapeake bay for fourth of july.This votec does have alot of torque thou. From a stand still if i floor it. You can feel the stern lifting out of the water and i'm up on plane in 13 seconds
 
Very cool:thumbsup: Have fun out there.
 
yeah we go down every year.We stay on the boat for about 5 days. You said about having the prop worked on. Well in my neck of the woods we don't have a prop shop.
 
lime4x4 said:
yeah we go down every year.We stay on the boat for about 5 days. You said about having the prop worked on. Well in my neck of the woods we don't have a prop shop.
Click to expand...
www.propmd.com He said its 20.00 to have a prop shipped to Calif. He is on the East Coast. I will be buying a cupped Bravo 3 prop through him. Saving some big $$
I live out in the boonies myself. Cupping a prop seems to help the holeshot and mid rpm cruise speeds also.
I do 90% of my boat shopping on line. Beats driving 110 miles to decent parts place. Which I usually have to order anyway :huh:
 
Thanks for the info.. Tonight while i was going thru my prop collection i found a 3 blade alum 16 X 13 pitch prop. Which i will give a try and c where my wot go up to
 
Make sure you bring your tools with you.
You will probably want to yank that 16 x 13 prop back off in the first couple of minutes:lol:

I have a 16 x 14 My cruise speed was like 17kts at 3000 rpm. Always in rough water.
CSR guys have been happy with 16 x16 Alum and 15.25 X 15 stainless. Thats with the 79 26' DA and early 80's 26'

steve661 has the same boat as yours. he is trying to dial his setup in. His WOT was like 4100rpm also
 
Tail Chaser 661 said:
Make sure you bring your tools with you.
You will probably want to yank that 16 x 13 prop back off in the first couple of minutes:lol:

I have a 16 x 14 My cruise speed was like 17kts at 3000 rpm. Always in rough water.
CSR guys have been happy with 16 x16 Alum and 15.25 X 15 stainless. Thats with the 79 26' DA and early 80's 26'

steve661 has the same boat as yours. he is trying to dial his setup in. His WOT was like 4100rpm also
Click to expand...

Mines still impaired:huh: 30 mph, 15.8 x 15, 3400 wot. I don't think it's the prop. Waiting on rotor for electronic ignition. New rebuilt quadrajet goes on next. When new numbers come in I'll let you know.
 
my original engine had a very hard time hitting 3800 rpm's using the 15.75 X 15 prop. After playing and trying different stuff over the past year. The only thing that made a huge improvement was installing the vortec engine.Tail chaser i'm not installing that prop till after vacation..I don't really want to mess with the boat while on the bay.
 
My Merc manual for my boat shows boats 24'-29' gross up to 5700lbs? :huh:
14.5 x 15 Stainless, 15.25 x 15Alum, 16x14 alum speed range 19-38mph
A 16 x 13 top speed 27 mph 6800 lb boat. 34' boat lenght.

I like Mercs or Volvo prop selector websites to play with the numbers.
There is a possibility, Valley props in Ventura Ca said some of Mercs props have too much blade area. :huh:It was a 15.5 x 15 he said I could not spin. I'm guessing he trims the trailing edge off the blade. Dia/Pitch stays the same. I was able to spin a 15 x 17 with a very tired engine 4000rpm. 5 yrs ago I got 4200 with the same prop.
Maybe the 26'DA and 268DA are completely different animals
Plenty of room for a NOS bottle :lol:

I'm with you steve, Change out all questionable items first.
Then dial in the prop. It should be very close now.:thumbsup:
 
well i got to try the 16X13 3 blade alum prop tonight. Boat got up on plane but i had to keep it at 4000 to 4100 rpm's to stay on plane. But i was able to hit 4600 wot rpm's. I'm going back to the 15.75X15 3 blade ss prop. Atleast with that prop i can stay on plane at 3300 to 3500 rpm's. Oh and max speed with the 16X13 was 30 mph
 
I had a 86 25 sundancer that I also put the new vortec engine in.really made a huge difference,went from an underpowered pig to very useable and efficient.it jumped right out of the hole.I usually ran at 3200 RPM's at 22-24 knots and noticed at 2800 it would fall off plane.I was also using the same mirage prop as you.leave it on there,mine ran best with that setup.the only thing I would caution is be nice to the Alpha,that Vortec is putting out 320 HP.Your at the limit for the drive.I never had a problem but my drive guy said be nice and you won't have issues.
 
lime4x4 said:
well i got to try the 16X13 3 blade alum prop tonight. Boat got up on plane but i had to keep it at 4000 to 4100 rpm's to stay on plane. But i was able to hit 4600 wot rpm's. I'm going back to the 15.75X15 3 blade ss prop. Atleast with that prop i can stay on plane at 3300 to 3500 rpm's. Oh and max speed with the 16X13 was 30 mph
Click to expand...
Lime what is the wot with the 15.75 x 15 and what is the max speed? thanks, Steve
 
stevea661 with the 15.75 X 15 mirage plus my max speed according to gps is 32.4 mph and my wot at 4100. Yeah the vortec engine is is great for my heavy boat. This is the best it ever performed in the 3 years that i've owned it.
ALso have a mercruiser alpha 1 out drive with a 1.5 ratio
 
Last edited:
Thanks lime:smt001
 
Hey guys, I am new to the boating scene and have a related question for the more knowledgeable people here. Have a 72 240 srv with a 350. Wot is around 4300 rpm amd getting about 27 mph out of it.
I have seen hydrofoils that claim to keep the boat on plane at a lower rpm and saves gas also among other benefits.
Do these work as advertised? And when you trim the outdrive at cruise will a hydrofoil effect the plane speed?
 
I have an 86 DA with 350-269 and a 16x13 prop which is supposed to be the right prop. I can stay on plane at 3200 rpms and get 18mph out of it. I top out at 4200 rpms and 26mph. Check the bottom of your boat for growth. You also need to get the bow down with your trim tabs and then raise the bow a touch with the out drive.
 
OK, just for an update...
I had a chance to check out my 1986 Weekender 268 350/260HP on a very flat Lake Erie this morning (which turned pretty lumpy after a few short hours). According to the GPS, I topped out at 33.6 MPH, 4200 RPM. Tabs were down full, outdrive trimmed up just a tad. I was pleased. She runs nice and smooth and quiet. 3000 RPMs is my favorite cruising "sweet spot"...approx. 21.5 MPH.
 
Hampton,
Depending on the conditions, I may experiment from time to time and raise the trim tabs up a bit while cruising, but in general my tabs are down most of the time. I've heard a guy who is a well-known Sea Ray "expert" in our area who said when he had his 268 if he could "trim the swim platform down, he'd have done that too". An exaggeration, I'm sure...but you get the idea. All in all, I like how my boat performs, handles, and stays on plane. :smt001
 
You must log in or register to reply here.

Forum statistics

Threads
113,204
Messages
1,428,513
Members
61,109
Latest member
Minnervos
Back
Top